Limitations to Starch Utilization in Barramundi (Lates calcarifer) as Revealed by NMR-Based Metabolomics

Abstract

Practical diets for commercial barramundi production rarely contain greater than 10% starch, used mainly as a binding agent during extrusion. Alternative ingredients such as digestible starch have shown some capacity to spare dietary protein catabolism to generate glucose. In the present study, a carnivorous fish species, the Asian seabass (Lates calcarifer) was subjected to two diets with the same digestible energy: Protein (P)-with high protein content (no digestible starch); and Starch (S)-with high digestible (pregelatinized) starch content. The effects of a high starch content diet on hepatic glycogen synthesis as well as the muscle and liver metabolome were studied using a complementary approach of 1 H and 2 H NMR. The hepatosomatic index was lower for fish fed high starch content diet while the concentration of hepatic glycogen was similar between groups. However, increased glycogen synthesis via the direct pathway was observed in the fish fed high starch content diet which is indicative of increased carbohydrate utilization. Multivariate analysis also showed differences between groups in the metabolome of both tissues. Univariate analysis revealed more variations in liver than in muscle of fish fed high starch content diet. Variations in metabolome were generally in agreement with the increase in the glycogen synthesis through direct pathway, however, this metabolic shift seemed to be insufficient to keep the growth rate as ensured by the diet with high protein content. Although liver glycogen does not make up a substantial quantity of total stored dietary energy in carnivorous fish, it is a key regulatory intermediate in dietary energy utilization.

On the Utilization of Dietary Glycerol in Carnivorous Fish - Part I: Insights Into Hepatic Carbohydrate Metabolism of Juvenile Rainbow Trout (Oncorhynchus mykiss) and European Seabass (Dicentrarchus labrax)

“…2 H NMR spectra were obtained following the acquisition parameters described in Rito et al (2018). Estimation of blood glucose and hepatic glycogen sources from 2 H 2 O derive from unique labeling patterns created by their common precursor G-6-P, following the metabolic model for positional 2 H-labeling shown in Figure 1 and described in detail in Palma et al (2020). The positional 2 H-enrichments were quantified by using the MAG methyl signals (MAG-CH 3 ) as intramolecular standard (Nunes and Jones, 2009) (representative spectrum is presented in Supplementary Figure S1).…”

Metabolomics in salmonid aquaculture research: Applications and future perspectives

“…However, the precise mechanisms are not yet resolved and is an area where salmon metabolomics could provide further insights. Metabolomics studies in salmonids should also explore the effects of dietary gelatinised starch on energy, AA and lipid metabolism in muscle and liver tissues as demonstrated in other teleosts 29,247–249 . Metabolomics also offers novelty to characterise new feed resources, to identify sustainable FO/FM replacement ingredients 250–254 and assess dietary imbalances 255 .…”

“…Metabolomics studies in salmonids should also explore the effects of dietary gelatinised starch on energy, AA and lipid metabolism in muscle and liver tissues as demonstrated in other teleosts. 29,[247][248][249] Metabolomics also offers novelty to characterise new feed resources, to identify sustainable FO/FM replacement ingredients [250][251][252][253][254] and assess dietary imbalances. 255 For example, fermented aquafeed, plant-based essential fatty acids and micro-algae products have been identified as sustainable alternatives to FM/ FO, since they offer nutritional and health benefits.…”

Effects of dietary plant and animal protein sources and replacement levels on growth and feed performance and nutritional status of market-sized turbot (Scophthalmus maximus) in RAS

“…However, compared to traditional feed ingredients such as fishmeal and soybean products, they differ often in quality, nutritional composition, digestibility of nutrients and availability of minerals (Glencross, 2016;Hua et al, 2019). This may affect growth, nutrient utilization and whole body composition (Bonaldo et al, 2015;Aragao et al, 2020) of carnivorous fish and lead to an altered energy metabolism and energy allocation (Palma et al, 2020).…”